A. Field of the Invention
The invention relates generally to connecting an interface to a serial bus, more particularly, to identifying an interface type from at least one identification line and switching the interface onto or off the serial bus depending on the interface type identified.
B. Background of the Invention
Present telecommunication systems employ a wide variety of connection interface types, such copper style, optical LW, Serial Module definition protocol, optical SW, for example. The systems include a variety of Fibre Channel systems to convert a Fibre Channel interface from one type to another. By way of example, by changing interface types a user can change a Fibre Channel interface on a product from copper to optical, or from optical to copper.
Often, these interface types carry data which must be transferred via a common bus within a communication device, such as a disc array controller. For example, a communication device may have a central processing bus for transmitting data between various semiconductors (e.g. DSPs, framers, de-packetizers) for performing processing steps on data packets. Hence, many of these components and/or interface types may share a common bus that may be sensitive to changes from one interface type to another interface type.
Gigabit Interface Converters (GBIC) are used in a variety of Fibre Channel systems to easily change (i.e. convert) a Fibre Channel interface from one type to another. The GBIC standard utilizes three TTL-compatible signal lines (MOD—DEF[2..0]) to specify at least eight GBIC types (“Module Definitions”). The table below explains the GBIC standard as presently implemented:
ModuleMOD—MOD—MOD—DefinitionDEF[0]DEF[1]DEF[2]Interpretation0NCNCNCGBIC not present1NCNCTTL LOWCopper Style 1 or 2connector, 1.0625 Gbm100-TW-EL-S or 100-TP-EL-S, active inter-enclosure connector andIEEE802.3 100BASE-CX2NCTTL LOWNCCopper Style 1 or 2connector, 1.0625 Gb,100-TW-EL-S or 100-TP-EL-S, active orpassive intra-enclosureconnection3NCTTL LOWTTL LOWOptical LW, 1.0625 Gb100-SM-LC-L4TTL LOWSERIALSERIALSerial module definitionCLKDATAprotocol5TTL LOWNCTTL LOWOptical SW, 1.0625 Gb100-M5-SN-I or 100-M6-SN-I6TTL LOWTTL LOWNCOptical LW, 1.0625 Gb100-SM-LC-L andsimilar to 1.25 GbIEEE802.3z 1000BASE-LX, single mode7TTL LOWTTL LOWTTL LOWOptical SW, 1.0625 Gb100-M5-SN-I or 100-M6-SN-I and 1.25 Gb,IEEE802.3z,1000BASE-SX
Module Definition 4 specifies a serial definition protocol, wherein MOD—DEF[1] is used to transmit serial clock signals and MOD—DEF[2] is used to serial data. If a host interface detects a Module Definition 4 GBIC, the serial may then be activated thereby transmitting via MOD—DEF[2..1].
Depending on the implementation, changing interface types in configurations such as GBICs may result in a highly undesirable bus lockup. GBICs that support Module Definition 3 (for example) have both MOD—DEF[1] and MOD—DEF[2] internally connected to a TTL low. If a Module Definition 3 type is inserted into a system capable of two wire serial (TWS) communication, it will hold both the serial clock and serial data lines to a TTL low, which will prevent the bus from functioning properly. Hence, a need exists for a method for connecting an interface to a serial bus depending on the interface type identified. Further, a need exists for a method that quickly and automatically isolates an interface from a serial bus when a serial interface type is removed from the interface.